Electrophoresis is the standard technique used in nucleic acid sequencing, the technique used to plot the human genome, as reported in Chemistry and Engineering News, p. 22-28, dated Mar. 14, 1988. That is, DNA fragments are electrophoresed. Because of their size, this requires the use of higher power than is needed for other applications. Power usage of as much as 70 watts is common. Such power generates tremendous heat and thermal gradients in the gel plate, with the highest temperature occurring in the center lanes. Conventional vertical electrophoresis units tend to be unsatisfactory for nucleic acid sequencing, since the temperature gradients formed during the process produce artifacts that make interpretation of the results difficult, and the labeled fragments do not form uniformly straight lines. Instead, the detectable bands have the appearance of "smiles", due to the center lanes progressing faster than they should.
One problem, therefore, prior to this invention, has been to construct a sequencer that gives uniformly straight lines in the autoradiogram. This in turn requires improved temperature distribution in the gel plate.
Yet another problem with prior gel plates has been a difficulty in detecting whether or not the sample-adding pipette is in proper position within the gel plate assembly, for dispensing sample. Because of the cleanliness that is required, it has often also been difficult to ascertain whether the cavity within which the gel is to be formed, is sufficently clean.